Coenzyme Q10 (CoQ10) is also referred to as ubidecarenone, ubiquinone-10 or the like, and has been utilized as a medicament such as a metabolic cardiotonic drug due to its specific physiological action. In addition, in Japan, the coenzyme Q10 can now be utilized in the application for food according to the revision in the classification of foods and medicines, and its application in the field of health-foods is expected. Especially the recent studies of CoQ10 have been very fruitful, and there have been reported myocardial protection action, prevention of carcinogenesis, anti-aging action, and LDL oxidation suppression in blood derived from anti-oxidative action of CoQ10, as well as suppression of elevation in blood pressure, amelioration in oxygen utilization efficiency in myocardial ischemia, ATP synthesis activation at myocardial mitochondria, cardiac function amelioration or the like. However, CoQ10 is a yellow to orange solid at an ordinary temperature, which is hardly dissolvable in water or alcohol, and is less likely to be dissolved in an oil, so that there are some disadvantages that its general-purpose for the utilization in the food use is very low, and the application to a beverage especially poses great limitation.
As a method for producing a CoQ10 preparation, there have been proposed a method for preparing an aqueous liquid preparation of a fat-soluble substance, comprising mixing a CoQ10, an emulsifying agent, a polyhydric alcohol and water, and thereafter subjecting the mixture to a high-pressure treatment (see, for example, JP 2000-212066 A), a method of solubilization using a polyoxyethylene sorbitan monooleate (see, for example, JP 2001-504343 A), and the like. However, the aqueous liquid preparation produced by the former method can temporarily obtain CoQ10 in the form of an aqueous liquid preparation by carrying out a treatment at an ultrahigh-pressure of 1000 kg/cm2, but its stability is poor and becomes white turbid or precipitates crystals of CoQ10. Also, in the latter method, the polyoxyethylene sorbitan monooleate is used, and the ethylene oxide-based surfactant is not preferable for the utilization in food use because highly toxic by-products are produced in the synthetic reaction during the production process.
In addition, as a preparation having enhanced bioabsorption ratio of the CoQ10, there has been proposed a mixture of a CoQ10 and an edible oil in which a CoQ10 is dispersed in the form of crystals, obtainable by adding a thermally dissolved CoQ10 in a heated edible oil, or adding a CoQ10 to an edible oil, thermally dissolving the mixture, and then cooling the mixture (see, for example, JP 2003-125734 A). However, this preparation cannot be directly added to an aqueous food.